Method of loading the hold of a vessel with dredging spoil

ABSTRACT

In the conventional method of loading a hold of a vessel with dredging spoil, in which a suspension of water and dredging spoil is admitted into the hold after the hold overflows until the required amount of dredging spoil is situated in the hold. Much dredging spoil flows into the outboard water. A more efficient filling operation is obtained when the suspension is deposited in a tube which is so kept in the hold that it is surrounded by the hold on all sides, and which is kept at such a depth in the hold that the bottom of the tube always remains above the level of the settled part of the spoil, while the tube penetrates into the liquid.

United States Patent METHOD OF LOADING THE HOLD OF A VESSEL WITH DREDGING SPOIL 3 Claims, 5 Drawing Figs.

US. Cl 214/152, 37/58, 114/26, 2l4/l5 B Int. Cl .L B63b 27/24 Field of Search 114/26, 76;

[56] References Cited UNITED STATES PATENTS 1,708,176 4/1929 Holly 214/13 UX 2,215,736 9/1940 Jones 214/14 FOREIGN PATENTS 1,111,519 5/1968 Great Britain 114/73 Primary Examiner--Gerald M. Forlenza Assistant ExaminerFrank E. Werner Attorney-Imirie, Smiley, Snyder & Butrum ABSTRACT: In the conventional method of loading a hold of a vessel with dredging spoil, in which a suspension of water and dredging spoil is admitted into the hold after the hold overflows until the required amount of dredging spoil is situated in the hold.

Much dredging spoil flows into the outboard water. A more efficient filling operation is obtained when the suspension is deposited in a tube which is so kept in the hold that it is surrounded by the hold on all sides, and which is kept at such a depth in the hold that the bottom of the tube always remains above the level of the settled part of the spoil, while the tube penetrates into the liquid.

PATENTED N 4 I973 I N VE NTOR JAN 66 KoNiNG Q "BQMU%@,W

ATTORF-JEY:

METHOD OF LOADING THE HOLD OF A VESSEL WITH DREDGING SPOIL This invention relates to a method of loading the hold of a vessel with dredging spoil, in which a suspension of water and dredging spoil is admitted into the hold, even after the latter overflows, until the hold has been completely or substantially completely filled with dredging spoil.

It is well known that in this conventional method the suspension deposited in the hold flows down in the form of a downwardly extending column of undiluted spoil having a high specific gravity and flows away mainly horizontally over the layer of dredging spoil which has settled at the bottom of the hold, a high flow velocity occurring as a result of the energy conversion, and then flows up along the wall and then flows over the top edge of said wall. In order to allow the maximum amount of dredging spoil to settle from this flow it has already been proposed to provide bulkheads in the hold, such bulkheads having closable openings at the bottom, and if interruptions should occur frequently to the supply and relatively coarse particles settle, clogging occurs as a result.

In modern suction dredgers, pumps having a very high output are provided in order to reduce the loading time, so that the flow of the spoil through the openings situated at depth below the settled sand is not fast enough.

The object of the invention is to ensure that an adequate amount of spoil can be handled while reducing the amount of dredging spoil which flows overboard.

To this aim the invention provides a method of loading a hold of a vessel with dredging spoil, in which a suspension of water and dredging spoil is admitted into the hold after the hold overflows until the required amount of dredging spoil is situated in the hold, wherein the suspension is deposited in a tube which is so kept in the hold that it is surrounded by the hold on all sides, and which is kept at such a depth in the hold that the bottom of the tube always remains above the level of the settled part of the spoil, while the tube penetrates into the liquid.

As a result of the higher weight per unit of volume of the suspension in the tube which is narrow with respect to the hold, the level is shifted so that the level in the tube is lower than in the hold. In conjunction therewith, the speed of flow extending horizontally from the bottom of the tube is lower. With the very much lower speed, dredging spoil from the horizontal flow of suspension has a greater tendency to settle, while the flow having this lower speed has less tendency to erode the top surface of the layer of dredging spoil which has settled at the bottom of the hold. The suspension flowing overboard thus has a reduced spoil content.

The invention further provides a method of loading a hold, wherein said tube is drawn up as the hold fills with settled dredging spoil, care being taken to ensure that the bottom edge of said tube remains just above the settled dredging spoil. Another preferred method according to the invention relates to the drawing up of the tube controlled in dependence on the load of the vessel. The load may be picked up by load pickups, providing signals to a computing unit controlling operation means for raising the tube. This last method can be advantageously applied to vessels having a large hold and overflow means, so that a constant tonnage can be loaded.

The invention also improves a vessel having a hold for the transportation of dredging spoil so that it is specially adapted for performing the method according to the invention. This vessel is characterized by a tube receiving the discharge pipe, said tube being open at the top and being surrounded by said hold on all sides, the space inside the tube communicating with the space of the hold, while the bottom edge of said tube has an adjustable depth in said hold.

The invention also provides an improved suction dredging installation, comprising a discharge pipe for filling at least one hold of a vessel, wherein the discharge pipe is provided with a tube which is connected to said discharge pipe and which can be so adjusted that the bottom edge of said tube penetrates into the liquid of said hold but remains above the settled dredging spoil of said hold, while the top of the tube communicates with atmosphere.

The features of the invention will be explained in detail with reference to the accompanying drawings wherein:

FIG. 1 is a diagrammatic side elevation of a preferred embodiment of a suction dredging installation according to the invention,

FIGS. 2a and 2b are enlarged details of other preferred embodiments,

FIGS. 3a and 3b are diagrammatic side elevations of preferred methods of filling barges.

The vessel 1 has a suction pipe 3 with a suction head 4 by means of which suspension of water with sand from the bed 12 is sucked up by a pump 5 and deposited into a tube 7 via the discharge pipe 6, said tube 7 being kept in the hold 2.

The advantage of the method according to the invention during filling of the hold 2 becomes apparent when the entire hold 2 has been filled with suspension 19, the suspension surface being indicated by reference 8. The tube 7 is so kept in the hold 2 that it is surrounded by the hold 2 on all sides, the said tube 7 being kept at such a depth in the hold 2 that the bottom edge 18 of the tube 7 always remains above the level 10 of the settled part 20 of the spoil, while the bottom edge 18 of the tube 7 penetrates into the liquid 19.

During further filling, the level of the suspension 21 in the tube 7 is clearly shifted to a level 80 which is lower than the level 8 of suspension 19. This situation is maintained as a result of the small free space between the spoil level 10 and the bottom edge 18 of the tube 7, until the required amount of dredging spoil is present in the hold 2.

The vessel 1 is provided with valves 9 for discharging the dredging spoil from the hold 2.

In each of the preferred embodiments shown in FIGS. 2a and 2b the tube 7 is suspended from the discharge pipe 6.

In FIG. 2a the discharge pipe 6 comprises a stationary part 6a, a swingable end part 6c communicating with said part 6a via a flexible tube part 6b and pivotably attached to said part 6a by means of hinges 16, a jack 13 operating the swinging movement of said end part 6c. The bottom edge 18 moves from the position 18 upwards during swinging movement of end part 6c.

In FIG. 2b the tube part 7b of telescopic tube 7 is fixed rigidly to the tube 6. The lower tube part 7a having a bottom edge 18 is telescopically slidable on said tube part 7b, a jack 13 operating the sliding movement of tube part 7a.

The height of the spoil level 10 in the hold can be determined accurately by load gauges and a computer unit. This will be explained with reference to FIG. 2a.

As shown in FIG. 2a the load of the vessel is measured with a pressure pickup 22 arranged at the bottom of the suction dredger l and comprising a pressure-sensitive membrane 33, limiting a chamber 17 connected to the outboardwater 32. The pressure pickup picks up the pressure corresponding with its depth in the outboardwater 32, which is a measure for the draught of the suction dredger l and the weight of the load.

The pressure pickup 22 provides signals to receiver 3I. From these signals the draught of the vessel 1 is determined in calculating unit 30 providing signals to the draught indicator 28. The calculating unit 30 preferably also provides signals concerning the draught to the signal converter 29. This signal converter 29 provides signals to the control valves 27 for controlling the hydraulic jack 13 of tube 7.

The invention can also advantageously be applied to the filling of barges 15 by means of a suction dredger 14 as will be apparent from FIGS. 3a and 3b.

In FIGS. 3a and 3b a barge 15 having a hold 2 is filled with a suspension of water and sand from the bed 12, which is sucked up by pump 5, a suction dredger 14 through a suction head 4 and suction pipe 3 and which is discharged through discharge pipe 6 into a tube 7.

In FIG. 3a a tube 7 consists of a tube part 7b connected to the barge 15 by means of studs 25 and of a slidable lower tube part 7a having a lower edge 18, a jack 13 operating the sliding movement of said tube part 7a.

In FIG. 3b the discharge pipe consists of a stationary pipe part 6a, a midpipe part 6b pivotably connected to pipe part 60 and an end pipe part 6c pivotably connected to pipe part 6b, jacks 13 operating the swinging movement of pipe parts 61; and 6c. A tube 7 is fixed to end pipe part 6c.

The tube 7 communicates with atmosphere through the gap 26 between discharge pipe 6 and tube 7.

What I claim is:

l. A method of depositing and rapidly settling sand in the hold of a vessel from a suspension of sand in water directed into the hold as a stream, which comprises the steps of:

a. filling the hold with the suspension until the hold contains a quantity of settled sand and an overlying level of water in substantially overflowing relation to the hold;

b. at least after setup (a discharging the suspension stream downwardly into the hold within the confines of a tube having an open lower end projecting below the overflow level of the hold and having an upper end in free communication with ambient atmosphere, and maintaining the lower end of the tube above but in sufficiently close proximity to the level of the settled sand that the level of material in said tube is significantly lower than the level of the overflowing water; and

c. continuing the overflow filling of step (b) while raising the lower end of the tube to retain the aforesaid positioning thereof with respect to the rising level of settled sand until a selected quantity of sand has been settled in the hold.

2. The method according to claim 1 including the step of measuring the draught of the vessel and controlling the raising of the lower end of the tube in response to such measurement.

3. The method of filling the hold of a vessel with sand settled from a suspension of sand in water after the hold has been filled to capacity with the suspension so that the hold contains a bed of settled sand below the overflow level of the hold and is overflowing predominantly with water from the hold. which comprises the steps of: 

1. A method of depositing and rapidly settling sand in the hold of a vessel from a suspension of sand in water directed into the hold as a stream, which comprises the steps of: a. filling the hold with the suspension until the hold contains a quantity of settled sand and an overlying level of water in substantially overflowing relation to the hold; b. at least after step (a ) discharging the suspension stream downwardly into the hold within the confines of a tube having an open lower end projecting below the overflow level of the hold and having an upper end in free communication with ambient atmosphere, and maintaining the lower end of the tube above but in sufficiently close proximity to the level of the settled sand that the level of material in said tube is significantly lower than the level of the overflowing water; and c. continuing the overflow filling of step (b) while raising the lower end of the tube to retain the aforesaid positioning thereof with respect to the rising level of settled sand until a selected quantity of sand has been settled in the hold.
 2. The method according to claim 1 including the step of measuring the draught of the vessel and controlling the raising of the lower end of the tube in response to such measurement.
 3. The method of filling the hold of a vessel with sand settled from a suspension of sand in water after the hold has been filled to capacity with the suspension so that the hold contains a bed of settled sand below the overflow level of the hold and is overflowing predominantly with water from the hold, which comprises the steps of: a. discharging a stream of suspension into the hold at such a rate that sand tends to overflow the hold with the overflowing water; and b. forming a confined column of such stream from a level just above the level of the settled bed to a level below the overflow level of the hold by confining the discharge of such stream into tube means having an open lower end disposed and raised to maintain such level just above the settled sand and having an open upper end projecting above said overflow level. 